The present invention relates to: an image processing method and an image processing apparatus for performing determination process whether an obtained document image is similar to a preliminary reference image; and an image forming apparatus and an image reading apparatus employing this image processing apparatus.
Proposed methods for reading a document with a scanner and then determining whether the read document image is similar to a preliminary reference image include: a method in which keywords are extracted from an image read by an OCR and then pattern matching is performed on the basis of the extracted keywords; and a method in which documents of determination target are restricted to formatted documents with ruled lines and pattern matching is performed on the basis of information concerning the ruled lines extracted from the read document.
Further, in another method, important documents, confidential documents, and the like are preliminarily stored as reference images. Then, when the read document image is determined as being similar to a reference image, copying of the read document is inhibited so that forgery is prevented and security is improved.
Nevertheless, since a technique of pattern matching is used in the similarity determination, a problem arises that even a document image generated by applying a processing function such as color conversion, scaling, and trimming onto a read document image is undesirably determined as being similar to a reference image so that copying of the document is not permitted.
Thus, a copying apparatus is proposed in which when an inputted image (document image) is determined as an image the image formation (e.g., copying) of which is inhibited, exact formation of the inputted image is inhibited, while when the extent of edit processing performed under the instruction of a user exceeds a predetermined level, the edited inputted image is formed exactly. By virtue of this, even for a document the copying of which is inhibited, copying operation is executed when the copying is performed in a state that various copying functions provided in the copying apparatus are simultaneously utilized so that the result is clearly distinctive from the document (see Japanese Patent Publication No. 3028490).